Fertilizing Hydrangea Paniculata 
When it comes to fertilizing Paniculata hydrangeas, such as 'Pee Gee', Limelight', and 'Pinky Winky', you can use a well-balanced shrub and tree fertilizer or a mild organic plant food or manure-based fertilizer or compost. If a non-organic shrub and tree type fertilizer is used, make sure it's slow-release. You don't want to create too much foliage growth too quickly or you might end up with more foliage and less or smaller blooms.
When To Fertilize?
I would recommend fertilizing Hydrangea paniculata in spring, when new growth begins to emerge. If using an organic plant food, which will be more mild, you can fertilize two or three times during the active growth season. Remember, fall is the time for hydrangeas to begin preparing for dormancy so stop any feeding or fertilization at a point two months prior to first frost in your area. Fertilizing beyond this time might stimulate new growth that could be damaged by cold temperatures.
How Much Fertilizer?
The amount of fertilizer used per plant will vary with the size of the plant and the type of fertilizer or plant food used. Always follow instructions on product label for application rates. When fertilizing a newly planted shrub, you can broadcast the fertilizer on top and around the root ball. When fertilizing larger established shrubs, broadcast fertilizer around the perimeter of the outermost branches.
Other Fertilization Tips
Never fertilize a plant that looks sick or wilted. If a plant is struggling due to a disease or root problems, the fertilizer might add stress. Consult with your local nurseryman, or use Ask Experts here in Gardenality, to find the cause and a cure for the problem before adding fertilizer.
